// 2025/3/27
// 过河卒

#include <iostream>
#include <memory>
#include <vector>
using namespace std;

bool isDanger(int x, int y, int i, int j)
{
    int a = max(x - i, i - x);
    int b = max(y - j, j - y);
    return (a + b == 0) || (a + b == 3) && x != i && y != j;
}

int main() {
    int n, m, x, y;
    cin >> n >> m >> x >> y;
    vector<vector<long long>> dp(n + 1, vector<long long>(m + 1, 0));
    for(int i = 0; i <= n && !isDanger(x, y, i, 0); i++)
        dp[i][0] = 1;
    for(int j = 1; j <= m && !isDanger(x, y, 0, j); j++)
        dp[0][j] = 1;

    for(int i = 1; i <= n; i++)
    {
        for(int j = 1; j <= m; j++)
        {
            if(!isDanger(x, y, i, j))
            {
                dp[i][j] = dp[i - 1][j] + dp[i][j - 1];
            }
        }
    }
    cout << dp[n][m] << endl;
}
// 64 位输出请用 printf("%lld")